This satin dress from an LA-based brand has many similar features to an adult gownsweetheart neckline, fit-and-flare silhouettewith a playful touch

Groom Wearing a Green Jacket, Bolo Tie, Blue Jeans and Cowboy Hat Bride in Short White Dress, Cowboy Boots and Hat With Ladies Sitting on Western Bar Rustic Bride with Wedding Dress, Down Hairstyle and White Cowboy Boots Short Pale Blue Chiffon Dresses and Cowboy Boots Bride Hugging and Smiling With Welcome Party Guests Sage and Tangerine Wedding Invitation Suite With Cowboy Elements Bride in Short White Dress and Cowboy Hat, Groom in Cowboy Hat Leading Guests, Outdoors Rustic and Bohemian Wedding Invitation for Texas Wedding Bride in Short White Dress and Groom in Jeans, Cowboy Boots, Hats Kiss Under String Lights Cowboy-Inspired Invitation Suite for Wedding at Saddle Wood Farms in Murfreesboro, Tennessee White Cowboy Boots with Fire Design Flower Girls with Baskets and Cowboy Boots Bride Wearing White Dress With Long Tassels and Silver Glitter Cowgirl Boots Custom Pink Cowboy Boots With Lightning Designs for the Bride The Bride's Bohemian White Wedding Boots Rustic, Eclectic Painted Boots with Colorful Cactus Design Wedding Party Processional at Prospect Park in Brooklyn Colorful Bouquet and Blue Cowboy Boots Vintage Mexican Tunic Wedding Dress Bride and Guests Showing Off Their Unique Cowgirl Boots Sage-Colored Escort Cards Held Up by Mini Gold Cowboy-Boot Figurines Bride and Bridesmaids in Casual Dresses and Boots Sitting on Western Bar at Rehearsal Dinner Stone Architecture Outside Venue

Outer fabric is a semi-sheer with pinstripes
ATTIC's core service is free for all to use
I couldnt actually find any balloon dress sewing patterns for adults Im afraid if you know of any, do let me know in the comments and Ill add them in